1. Field of the Disclosure
This disclosure generally relates to a biometric detection module and, more particularly, to a biometric detection module with denoising function.
2. Description of the Related Art
Conventional pulse oximeters utilize a noninvasive method to monitor the blood oxygenation and the heart rate of a user. A pulse oximeter generally emits a red light beam (wavelength of about 660 nm) and an infrared light be am (wavelength of about 910 nm) to penetrate a part of the human body and detects an intensity variation of the penetrating light based on the feature that the oxyhemoglobin and the deoxyhemoglobin have different absorptivities in particular spectrum, e.g. referring to U.S. Pat. No. 7,072,701 entitled “Method for spectrophotometric blood oxygenation monitoring”. After the intensity variations, e.g. photoplethysmographic signals or PPG signals, of the penetrating light of the two wavelengths are detected, the blood oxygenation can then be calculated according to an equation: Blood oxygenation=100%×[HbO2]/([HbO2]+[Hb]), wherein [HbO2] is an oxyhemoglobin concentration; and [Hb] is a deoxyhemoglobin concentration.
Generally, the intensity variations of the penetrating light of the two wavelengths detected by a pulse oximeter will increase and decrease with heartbeats. This is because blood vessels expand and contract with the heartbeats such that the blood volume that the light beams pass through will change to accordingly change the ratio of light energy being absorbed. Therefore, the absorptivity of blood of different light spectra can be calculated according to the intensity information changing continuously so as to calculate the physiology information, e.g. the oxyhemoglobin and deoxyhemoglobin concentrations, respectively. Finally, the blood oxygenation can be calculated according to the above equation.
However, as the pulse oximeter detects the intensity variation of the penetrating light passing through body tissues, different intensity signals will be detected by detecting different parts of the human body. In addition, when the part of the human body being detected has a relative movement with respect to the pulse oximeter, a disturbed signal can be detected such that it is not possible to calculate correct physiology information. Therefore, a clear PPG signal is difficult to be detected under a condition of a non-static state.